As is known, these articles are obtained by laying a sheet of impermeable material over a sheet of permeable material (of non-woven fabric) and interposing an absorbent pad between the two sheets.
The absorbent article also comprise further accessory components, such as side tabs for fastening the nappy round the wearer's waist.
Generally, a prior art machine of this kind comprises a feed line for advancing a continuous web of material for making the absorbent articles and which is subsequently cut into the individual absorbent articles.
More specifically, the side tabs are applied to the continuous web along predetermined stretches so that when the web is cut, each absorbent article has at least one pair of side tabs.
Patent application WO2010001361A1, in the name of the same Applicant as this invention, describes a machine for making absorbent articles of the above mentioned kind.
The machine comprises a unit for forming pairs of side tabs and applying these pairs to the continuous web.
The unit comprises a device for cutting a continuous tape into individual side tabs, a first and a second roller, both located downstream of the cutting device, for picking up respective individual side tabs, and a roller, located downstream of the pickup rollers, for receiving the individual side tabs and capable of forming the pairs of side tabs which will be applied to the continuous web.
An accelerator roller picks up the pairs of side tabs from the receiving roller and conveys them in step to apply them to the continuous web.
In order to space the individual side tabs picked up from the continuous tape until they are positioned at a predetermined reciprocal distance based on the waistline of the absorbent articles, the first and second pickup rollers and the receiving roller are equipped with respective suction pads slidable along a direction parallel to the axis of rotation of the rollers.
More specifically, the first and the second pickup rollers initially translate the respective side tabs to position them at a distance which is smaller than the predetermined reciprocal distance based on the waistline, after which the receiving roller further spaces the side tabs of each pair until reaching that reciprocal distance.
This unit for forming and applying the side tabs has several disadvantages, however.
In effect, in order to meet market requirements for increasingly higher machine productivity, the need has arisen to increase the feed speed of the continuous web of nappies and, consequently, the speed of rotation of the rollers making up the unit for forming and applying the pairs of side tabs.
On account of the slidable suction pads, however, the first and second pickup rollers and the receiving roller are limited in their speed and cannot keep up with the high feed speed of the continuous web which the side tabs have to be applied to.